A Study of the Relationship between the Electrocardiogram and Hemodynamics in the Fetal Lamb during Asphyxia

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Abstract
Progressive changes in the S-T interval of the fetal ECG were studied in 22 lamb fetuses, acutely exteriorized and submitted to graded hypoxia. The ECG changes were studied to correlate them with cardiovascular function, as measured by heart rate, mean arterial pressure, end diastolic pressure and combined cardiac output, estimated by the thermodilution method, as well as with blood gases and acid-base status. Close correlations were obtained between PaO2 [arterial O2 partial pressure], pH and base deficit and the severity of ECG changes, graded according to scoring system. Alterations in the ECG pattern consistently preceeded signs of failing cardiovascular function. The hypoxic ECG changes were regarded as a sign of myocardial glycolysis. Similar progressive ECG changes were induced by isoprenaline injections. Progressive changes of the S-T interval of the fetal ECG contained information about fetal hypoxic stress before signs of failing cardiovascular function were seen.